Recently, lasers have been used in industrial production, particularly for welding, cutting, and surface treatment. In practice laser welding technology is increasingly gaining importance because of the high precision and processing speeds that can be achieved, the low thermal stress on the workpiece, and the high degree of automation which is possible. Current laser welding systems often use a CO2 (carbon dioxide) laser which produces a light beam having a wavelength of 10.6 μm (micro meters), or a solid-state device such as the Nd:YAG laser (Neodymium Yttrium Aluminum Garnet) laser, which produces a light beam having a wavelength of approximately 1.064 μm.
However, light from a CO2 laser may not couple with or be efficiently absorbed by certain metals and alloys. For example, the higher wavelength light of typical CO2 lasers may be significantly reflected by metals and alloys such as titanium, steel, etc. at room temperature. Similarly, YAG lasers that are often used for low power (<500 W (watts)) welding applications may not couple well or be efficiently absorbed by metals such as copper, gold, aluminum, etc. at room temperature.
Current laser welding systems typically compensate for poor absorption by increasing the peak power of the laser pulse to overcome the metal's initial resistance to coupling at room temperature. The absorption significantly increases when the metal reaches its melting temperature. However, before reaching the melting temperature the use of a high energy pulse may result in considerable inefficiency in that a significant portion of the laser beam may not be absorbed during the onset of the pulse. In addition, once the laser pulse couples with the material, the high peak power may add too much energy and cause the material to splash (radiate drops of molten metal) or cause unwanted vaporization of the metal and alloy components. The undesirable inefficiency and splashing may lead to inconsistent weld results.